UNANSWERED WORDS, ALPTUĞ ÖZEL, 503111302, 2nd WEEK, 11.03.2012

Automated guided vehicles (past)

Automated Guided Vehicles( AGVs) have a tremendous range of automated capabilities. Many systmes are called upon to go up and down ramps, open and close automatic doors, cross drawbridges, run outside, use elevators and perform advanced automatic loading and unloading functions. These capabilities give a materials handling engineer a powerful tool to use in solving horizantal materials transportataion problems.

(Raymond A. Kulwiec, Materials handling handbook,2nd edition, page275)

Automated guided vehicles (AGVs) (new) (beter) (group: automative)

These are battery-powered, driverless vehicles for automatic transport of parts and tooling on the shop flor. These move on fixed paths laid underneath the factory flor, and transport material from the workstations to storage locations., load stations, etc. Though the path of travel is laid underneath the factory flor, it is made of segments which allow the AGV to have a flexible path. These are one of the first choices for automating the material movement. A class of AGVs called rail-guided vehicles have fixed rails on which they move. This is far more restricted in terms of the path the RGV can take and service only a few workstations.

(P.N.RAO, Cad/Cam Principles and Applications,3rd Edition, page:603)

DNC (past)

Several machines are controlled directly step by step by a central mainframe computer. In this system the operator has access to the central computer through a remote terminal. With DNC, the status of all machines ina manufacturing facility can be monitored and assesed from a central computer. However DNC has a crucial disadvantage: If the computer shuts down all of the machines become inoperative. A more recent definition of DNC is distributed numerical control in which a central computer serves as the control system over a number of individual CNC machines having onoard microcomputers. This system provides large memory and computational facilities and offers flexibility while overcoming the disadvantage of direct numerical control.
(Serope Kalpakjian- Steven R. Schmid p:1155)

DNC (new) (beter) (group: manufacturing)

The technology of DNC started in early 1960s itself as an attempt to feed the numerical data directly into the machine by avoiding punched tape. The attempt has succeeded due to use of the computer for data feding, storage, and control of the NC machine tool.DNC can be defined as a type of manufacturing system in which several  NC and CNC machines are operated/controlled by a competer.

Direct numerical control is a form of NC machine in which a number of machines are controlled by a single competer directly. The tape reader, the least reliable component of CNC is omitted. Depeding on the computing capability, memory, access or transfer rate of data’s sinle computer have “n“ number of machines to be controlled. DNC computer provides the instruction to the various machines on demand and on-line through a communication line. DNC also has feedback data cpllection from the machine tool that it controls.

  (Alavudeen & Venkateshwaran, Computer Integrated Manufacturing, page: 201)

G-Code (Past)

 The G-Code is also called preparatory code or word. It is used to prepare the MCU for control functions. It indicates that a given control function is requested or that a certain unit or default be taken. There are modal functions and nonmodal functions. Modal functions are those do not change after they have been specified once, such as unit selection. Nonmodal functions are active in the block where they are specified.

(Computer Aided Manufacturing, T.Chang, R.A. Wysk, H.Wang, Second Edition, Prentice Hall International Series, 1998, Page: 365 )

G-Code (New) (better) (group: manufacturing)

G-Code is the language that the CNC understands in order to move its axes and perform operations. Also known as RS-274D, it is the Standard for numerically controlled machines and was developed by the Electronic Industry Association in the early 1960s.

G-Code was developed and first used with the original punched paper tape. The basic unit of the program is called a “block”, wihich is seen in printed form as a “line” of text. Each block can contain one or more”words”, which consist of a letter, describing a setting to be made, or a function to be performed, followed by a numerical field, supplying a value to that function. Various words can be combined to specify multi-axis moves, or perform special functions.

Descriptors preceded by the percent sign(%) or bound by parentheses are text or comments that are ignored by the machine. Their sole purpose is to add comments and clarity to the code.

G-Code can be entered manually using a text editor but these days is is usually produced by a post processor directly from the CAM software.

(Alain Albert, Understanding CNC Routers, 1st Edition, page: 80)